Citizen science reveals first comprehensive snapshot of the oral microbiome through age and lifestyle factors

Oral health is connected to the entire human body. For this reason, saliva contains a lot of useful information. The results of the citizen-science project ‘Saca la Lengua’ provide a dictionary that helps interpret the language of the oral microbiome so that, one day, using a saliva test could be as routine as blood or urine tests. The study analyzed the saliva of 1,648 people between 7 and 85 years of age located all over Spain. The study found that teenagers have a highly biodiverse oral microbiome that varies greatly between individuals. Middle-aged people had lower biodiversity as well as a generally homogeneous composition, representing a stage of high stability. From the age of 60, biodiversity and the differences between individuals increased considerably due to the establishment of rare opportunistic species, almost all of which are linked to oral diseases such as periodontitis. To understand the environmental and/or lifestyle characteristics that influence the oral microbiome, study participants completed a questionnaire that examined 80 different aspects of lifestyle habits, diet, hygiene and health. Factors associated with major changes in the oral microbiome were found to be linked to chronic diseases such as cystic fibrosis or conditions such as Down syndrome, followed by lifestyle habits such as smoking. Each of these factors changed the microbiome in a particular way, resulting in a specific signal. People with celiac disease, hypertension or those that used antibiotics also changed their oral microbiome in specific ways, although to a lesser extent.The impact of social and family relationships also influenced the composition of the oral microbiome. Members of the same family – for example, parents and children, or two brothers or sisters – have a more similar microbiome compared to two people from different families. The association exists even among members of the same class in school, a finding that leads us to hypothesise that sharing the same environment, even for a few hours a day, can significantly affect the oral microbiome.